A throttle passage is formed by providing a step portion by expanding an open end side of a refrigerant passage of the refrigeration cycle, placing a throttle passage member on the step portion, and squashing the throttle passage member using a columnar squashing jig to widen a rim of the outer periphery, thereby causing the throttle passage member to be fixedly engaged to an inner wall of the refrigerant passage. The throttle passage member has a simple shape formed only by machining a circular plate having a hole formed in a center thereof into a truncated conical shape, and therefore can be made at low cost. Throttle passage member is only squashed to be fixedly engaged in the refrigerant passage, and therefore can be easily formed.